The development of sex-specific characters is described for the deep sea North Atlantic/Arctic shrimp genus Bythocaris. A number of species were examined in the collections of Russian institutions including B. biruli, B. curvirostris, B. irene, B. leucopis and B. payeri. The pattern of size-specific variation in the masculine characters, i.e. the development of the modified appendix interna on the endopodite of the first pleopod and the appendix masculina do not indicate the presence of sex change (protandric hermaphroditism) in the life history.